A so-called flue gas-denitration apparatus that detoxifies nitrogen oxide by using ammonia or urea as a reducing agent and titanium oxide as catalyst has been widely used, world-wide, largely for the purpose of treating boiler flue gas. A variety of configurations for the catalyst has been used, including a plate like type wherein the catalyst is supported on a metal or ceramic lath, honeycomb type wherein a catalyst ingredient is formed into a honeycomb shape, and a granular type. In the field of flue gas-denitration, the former two types dominate the market.
As the substrate used for the plate type catalyst, stainless steel (SUS) is used, wherein a band-shaped stainless steel is generally formed into a metal lath. Specific examples of the stainless steel include ferrite stainless steel (SUS430) and austenite stainless steel (SUS304), and they have been used selectively for different purposes.